U.S. patent number 11,284,368 [Application Number 16/563,378] was granted by the patent office on 2022-03-22 for wireless communication method, control device, node, and terminal device.
This patent grant is currently assigned to Huawei Technologies Co., Ltd.. The grantee listed for this patent is HUAWEI TECHNOLOGIES CO., LTD.. Invention is credited to Liwei Ge, Yiping Qin, Jianbiao Xu, Youtuan Zhu.
United States Patent |
11,284,368 |
Xu , et al. |
March 22, 2022 |
Wireless communication method, control device, node, and terminal
device
Abstract
The present disclosure relates to coordinated multipoint
wireless communications methods. One example method includes
predicting a first delay difference between receiving, by a
terminal device, downlink data from a beam A of a first node and
receiving, by the terminal device, the downlink data from a beam B
of a second node, where the terminal device is located in a
coverage area in which the beam A intersects with the beam B, and
determining a first adjustment time period based on the first delay
difference, where the first adjustment time period is used to
adjust a transmission time in which the first node transmits the
downlink data to the terminal device by using the beam A.
Inventors: |
Xu; Jianbiao (Shanghai,
CN), Ge; Liwei (Shanghai, CN), Zhu;
Youtuan (Shanghai, CN), Qin; Yiping (Shanghai,
CN) |
Applicant: |
Name |
City |
State |
Country |
Type |
HUAWEI TECHNOLOGIES CO., LTD. |
Guangdong |
N/A |
CN |
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Assignee: |
Huawei Technologies Co., Ltd.
(Shenzhen, CN)
|
Family
ID: |
1000006189417 |
Appl.
No.: |
16/563,378 |
Filed: |
September 6, 2019 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20190394742 A1 |
Dec 26, 2019 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/CN2017/076111 |
Mar 9, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L
27/2662 (20130101); H04B 7/024 (20130101); H04W
56/0005 (20130101); H04W 56/0045 (20130101); H04L
27/2657 (20130101); H04W 72/042 (20130101); H04L
5/0048 (20130101) |
Current International
Class: |
H04W
56/00 (20090101); H04W 72/04 (20090101); H04L
27/26 (20060101); H04L 5/00 (20060101); H04B
7/024 (20170101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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102917393 |
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Feb 2013 |
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103037498 |
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Apr 2013 |
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CN |
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103298002 |
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Sep 2013 |
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CN |
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103427895 |
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Dec 2013 |
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CN |
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103875198 |
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Jun 2014 |
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CN |
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105324944 |
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Feb 2016 |
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CN |
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2014164234 |
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Oct 2014 |
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WO |
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2017007189 |
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Jan 2017 |
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WO |
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Other References
PCT International Search Report and Written Opinion issued in
International Application No. PCT/CN2017/076111 dated Jun. 29,
2017, 16 pages (with English translation). cited by applicant .
Extended European Search Report issued in European Application No.
17899268.1 dated Jan. 30, 2020, 8 pages. cited by applicant .
Office Action issued in Chinese Application No. 201780086075.8
dated Mar. 30, 2020, 20 pages (with English translation). cited by
applicant.
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Primary Examiner: Kassim; Khaled M
Attorney, Agent or Firm: Fish & Richardson P.C.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of International Application No.
PCT/CN2017/076111, filed on Mar. 9, 2017, the disclosure of which
is hereby incorporated by reference in its entirety.
Claims
What is claimed is:
1. A wireless communication method, used in a coordinated
multipoint system comprising a plurality of nodes, wherein the
method comprises: predicting a first delay difference between
receiving, by a terminal device, downlink data from a beam A of a
first node and receiving, by the terminal device, downlink data
from a beam B of a second node, wherein the terminal device is
located in a coverage area in which the beam A intersects with the
beam B, and wherein predicting the first delay difference
comprises: obtaining a second delay difference between receiving,
by the terminal device, a downlink pilot signal from the beam A of
the first node and receiving, by the terminal device, a downlink
pilot signal from the beam B of the second node; and predicting the
first delay difference based on the second delay difference; and
determining a first adjustment time period based on the first delay
difference, wherein the first adjustment time period is used to
adjust a transmission time in which the first node transmits the
downlink data to the terminal device by using the beam A, and
wherein a delay difference between receiving, by the terminal
device, the downlink data from the beam A and receiving, by the
terminal device, the downlink data from the beam B is less than a
predetermined value.
2. The method according to claim 1, wherein before the first node
transmits the downlink data to the terminal device by using the
beam A and the second node transmits the downlink data to the
terminal device by using the beam B, the downlink pilot signal from
the beam A of the first node and the downlink pilot signal from the
beam B of the second node are cell-level pilot signals.
3. The method according to claim 1, wherein when the first node
transmits the downlink data to the terminal device by using the
beam A and the second node transmits the downlink data to the
terminal device by using the beam B, the downlink pilot signal from
the beam A of the first node and the downlink pilot signal from the
beam B of the second node are user-level pilot signals.
4. The method according to claim 1, wherein the predicting a first
delay difference between receiving, by a terminal device, downlink
data from a beam A of a first node and receiving, by the terminal
device, the downlink data from a beam B of a second node comprises:
obtaining a third delay difference between receiving, by the first
node using the beam A, an uplink reference signal transmitted by
the terminal device and receiving, by the second node using the
beam B, an uplink reference signal transmitted by the terminal
device; and predicting the first delay difference based on the
third delay difference.
5. The method according to claim 4, wherein the method further
comprises: controlling the first node and the second node to
simultaneously transmit correction signals in an uplink/downlink
switching guard period; obtaining a time in which the first node
receives a correction signal sent by the second node and a time in
which the second node receives a correction signal sent by the
first node; and determining a fourth delay difference between an
intermediate radio frequency channel of the first node and an
intermediate radio frequency channel of the second node based on
the time in which the first node receives the correction signal
sent by the second node and the time in which the second node
receives the correction signal sent by the first node; and wherein
the predicting the first delay difference based on the third delay
difference comprises: predicting the first delay difference based
on the third delay difference and the fourth delay difference.
6. The method according to claim 1, wherein the method further
comprises: determining a second adjustment time period for the
first node based on the first adjustment time period, wherein the
second adjustment time period for the first node is used to adjust
a transmission time in which the first node transmits a user-level
pilot signal to the terminal device in the first node by using the
beam A.
7. A control device, used in a coordinated multipoint system
comprising a plurality of nodes, wherein the control device
comprises: at least one processor; and a non-transitory
computer-readable storage medium coupled to the at least one
processor and storing programming instructions for execution by the
at least one processor, wherein the programming instructions
instruct the at least one processor to: predict a first delay
difference between receiving, by a terminal device, downlink data
from a beam A of a first node and receiving, by the terminal
device, the downlink data from a beam B of a second node, wherein
the terminal device is located in a coverage area in which the beam
A intersects with the beam B, and wherein predicting the first de
lay difference comprises: obtaining a second de lay difference
between receiving, by the terminal device, a downlink pilot signal
from the beam A of the first node and receiving, by the terminal
device, a downlink pilot signal from the beam B of the second node;
and predicting the first de lay difference based on the second
delay difference; and determine a first adjustment time period
based on the first delay difference, wherein the first adjustment
time period is used to adjust a transmission time in which the
first node transmits the downlink data to the terminal device by
using the beam A, and wherein a delay difference between receiving,
by the terminal device, the downlink data from the beam A and
receiving, by the terminal device, the downlink data from the beam
B is less than a predetermined value.
8. The control device according to claim 7, wherein before the
first node transmits the downlink data to the terminal device by
using the beam A and the second node transmits the downlink data to
the terminal device by using the beam B, the downlink pilot signal
from the beam A of the first node and the downlink pilot signal
from the beam B of the second node are cell-level pilot
signals.
9. The control device according to claim 7, wherein when the first
node transmits the downlink data to the terminal device by using
the beam A and the second node transmits the downlink data to the
terminal device by using the beam B, the downlink pilot signal from
the beam A of the first node and the downlink pilot signal from the
beam B of the second node are user-level pilot signals.
10. The control device according to claim 7, wherein the
programming instructions instruct the at least one processor to:
obtain a third delay difference between receiving, by the first
node using the beam A, an uplink reference signal transmitted by
the terminal device and receiving, by the second node using the
beam B, an uplink reference signal transmitted by the terminal
device; and predict the first delay difference based on the third
delay difference.
11. The control device according to claim 10, wherein the
programming instructions instruct the at least one processor to:
control the first node and the second node to simultaneously
transmit correction signals in an uplink/downlink switching guard
period; obtain a time in which the first node receives a correction
signal sent by the second node and a time in which the second node
receives a correction signal sent by the first node; and determine
a fourth delay difference between an intermediate radio frequency
channel of the first node and an intermediate radio frequency
channel of the second node based on the time in which the first
node receives the correction signal sent by the second node and the
time in which the second node receives the correction signal sent
by the first node; and wherein the predicting the first delay
difference based on the third delay difference comprises:
predicting the first delay difference based on the third delay
difference and the fourth delay difference.
12. The control device according to claim 7, wherein the
programming instructions instruct the at least one processor to:
determine a second adjustment time period for the first node based
on the first adjustment time period, wherein the second adjustment
time period for the first node is used to adjust a transmission
time in which the first node transmits a user-level pilot signal to
the terminal device in the first node by using the beam A.
Description
TECHNICAL FIELD
This application relates to the communications field, and more
specifically, to a wireless communication method, a control device,
a node, and a terminal device.
BACKGROUND
Because there are abundant spectrum resources and a massive antenna
array is easy to deploy, a millimeter wave band gradually becomes
one of key candidate technologies of 5G. Particularly, because an
antenna array spacing at the millimeter wave band is smaller,
massive multiple-input multiple-output (MIMO) may be deployed on a
base station (BS) side, and at least four antennas may also be
usually deployed on a terminal device (MS) side.
However, due to a ratio of a line of sight (LOS) path component on
a high-frequency channel, for a single node (Transmission point,
TP) and a single terminal device, a spatial degree of freedom is
mainly limited by the channel, and spatial resolution and spatial
multiplexing potential of the massive antenna array cannot be
effectively realized.
In a coordinated multipoint technology, spatial degrees of freedom
and a power superposition gain of a plurality of nodes are
obtained, so that the spatial resolution and the spatial
multiplexing potential of the massive antenna array on the
high-frequency channel are effectively realized, thereby
effectively improving system spectral efficiency. However, in a
coordinated transmission mode, in addition to a multipath delay
spread inherent in a single-cell channel, there is an inter-TP
delay difference between a plurality of nodes. The delay difference
between nodes includes an air interface transmission delay
difference and an intermediate radio frequency (IRF) timing error.
The delay difference between nodes increases a multipath delay
spread of a coordinated equivalent channel. Therefore, when a ratio
of the inter-TP delay difference to a cyclic prefix (CP) reaches a
specific value, the multipath delay spread of the coordinated
equivalent channel exceeds the CP, interference such as orthogonal
frequency division multiplexing (OFDM) intersymbol interference
(ISI) is introduced, and a coordinated range shrinks.
A long term evolution (LTE) system is mainly specific to a low
frequency, an OFDM subcarrier spacing is 15 kHz, and a
corresponding CP length is about of a magnitude of 5 .mu.s. In a 5G
high-frequency system, to resist a larger frequency offset, a
subcarrier spacing needs to be increased (to a magnitude of 150
kHz). Correspondingly, in the 5G high-frequency system, a magnitude
of a CP length is reduced by 10 times compared with the magnitude
of the CP length in the LTE system. Consequently, a ratio of an
inter-TP delay difference to a CP is larger, and there is a higher
probability that a delay spread of a coordinated equivalent channel
exceeds the CP. Therefore, a problem to be urgently resolved is how
to reduce the delay difference between nodes, reduce the
probability that the delay spread of the coordinated equivalent
channel exceeds the CP, and avoid interference such as ISI between
OFDM symbols and shrinkage of a coordinated range.
SUMMARY
This application provides a wireless communication method and a
device, to implement a beam-level signal transmission
pre-adjustment on a node side. As a result, a delay difference
between receiving, by the terminal device, downlink data from a
beam A of a first node and receiving, by the terminal device, the
downlink data from a beam B of a second node is less than a
predetermined value. This resolves an ISI interference problem and
a coordinated area shrinkage problem that are introduced due to an
inter-TP air interface transmission delay difference and
intermediate radio frequency channel timing error in a coordinated
technology, thereby effectively increasing a coordinated area and a
coordinated gain particularly in a scenario of a shorter CP in a 5G
high-frequency system.
According to a first aspect, this application provides a wireless
communication method, used in a coordinated multipoint system that
includes a plurality of nodes, where the method includes:
predicting a first delay difference between receiving, by a
terminal device, downlink data from a beam A of a first node and
receiving, by the terminal device, the downlink data from a beam B
of a second node, where the terminal device is located in a
coverage area in which the beam A intersects with the beam B; and
determining a first adjustment time period based on the first delay
difference, where the first adjustment time period is used to
adjust a transmission time in which the first node transmits the
downlink data to the terminal device by using the beam A, so that a
delay difference between receiving, by the terminal device, the
downlink data from the beam A and receiving, by the terminal
device, the downlink data from the beam B is less than a
predetermined value.
Therefore, in this application, the first delay difference between
receiving, by the terminal device, the downlink data from the beam
A of the first node and receiving, by the terminal device, the
downlink data from the beam B of the second node is predicted, and
the transmission time in which the first node sends the downlink
data to the terminal device by using the beam A is determined based
on the first delay difference, to implement a beam-level signal
transmission pre-adjustment on a node side. As a result, a delay
difference between arrival, at the first terminal device, of the
downlink data sent by the first node to the first terminal device
and arrival, at the first terminal device, of the downlink data
sent by the second node to the first terminal device is less than
the predetermined value. This resolves an ISI interference problem
and a coordinated area shrinkage problem that are introduced due to
an inter-TP air interface transmission delay difference and an
inter-TP IRF timing error in a coordinated technology, thereby
effectively increasing a coordinated area and a coordinated gain
particularly in a scenario of a shorter CP in a 5G high-frequency
system.
Optionally, in an implementation of the first aspect, the
predicting a first delay difference between receiving, by a
terminal device, downlink data from a beam A of a first node and
receiving, by the terminal device, the downlink data from a beam B
of a second node includes: obtaining a second delay difference
between receiving, by the terminal device, a downlink pilot signal
from the beam A of the first node and receiving, by the terminal
device, a downlink pilot signal from the beam B of the second node;
and predicting the first delay difference based on the second delay
difference.
Optionally, in an implementation of the first aspect, the obtaining
a second delay difference between receiving, by the terminal
device, a downlink pilot signal from the beam A of the first node
and receiving, by the terminal device, a downlink pilot signal from
the beam B of the second node includes: obtaining the second delay
difference between sending, by the terminal device, the downlink
pilot signal to the terminal device on a first path of the beam A
of the first node and sending, by the second node, the downlink
pilot signal to the terminal device on a first path of the beam B.
The first path is usually a line of sight (LOS) path. When there is
no line of sight path on the beam A, the first path is a non-line
of sight (NLOS) path with a shortest transmission distance.
Optionally, in an implementation of the first aspect, before the
first node transmits the downlink data to the terminal device by
using the beam A and the second node transmits the downlink data to
the terminal device by using the beam B, the downlink pilot signal
is a cell-level pilot signal.
In this case, the first delay difference is determined based on the
second delay difference between receiving, by the terminal device,
the cell-level pilot signal from the beam A of the first node and
receiving, by the terminal device, the cell-level pilot signal from
the beam B of the second node. Therefore, before the downlink data
is transmitted, the first adjustment time period used for sending,
by the first node, the downlink data to the first terminal device
is determined based on the first delay difference, so that the
delay difference between receiving, by the terminal device, the
downlink data from the beam A and receiving, by the terminal
device, the downlink data from the beam B is less than the
predetermined value.
Optionally, in an implementation of the first aspect, when the
first node transmits the downlink data to the terminal device by
using the beam A and the second node transmits the downlink data to
the terminal device by using the beam B, the downlink pilot signal
is a user-level pilot signal.
In this case, the first delay difference is determined based on the
second delay difference between receiving, by the terminal device,
the user-level pilot signal from the beam A of the first node and
receiving, by the terminal device, the user-level pilot signal from
the beam B of the second node. Therefore, when the downlink data is
transmitted, the first adjustment time period used for sending, by
the first node, the downlink data to the first terminal device is
determined based on the first delay difference, so that the delay
difference between receiving, by the terminal device, the downlink
data from the beam A and receiving, by the terminal device, the
downlink data from the beam B is less than the predetermined
value.
Optionally, in an implementation of the first aspect, the
cell-level pilot signal or the user-level pilot signal or both are
decoupled, and time division transmission may be performed on the
cell-level pilot signal and/or the user-level pilot signal by using
different subframes.
In this case, the cell-level pilot signal or the user-level pilot
signal or both are decoupled, so that a transmission timing
pre-adjustment to the user-level pilot signal does not affect
transmission of the cell-level pilot signal.
Optionally, in an implementation of the first aspect, when a
plurality of first terminal devices that perform frequency division
multiplexing are in the coverage area in which the terminal device
is located and in which the beam A of the first node intersects
with the beam B of the second node, the method further includes:
obtaining second delay differences of the plurality of first
terminal devices that perform frequency division multiplexing, and
estimating the first delay difference based on an average value of
the second delay differences.
Optionally, in an implementation of the first aspect, the
predicting a first delay difference between receiving, by a
terminal device, downlink data from a beam A of a first node and
receiving, by the terminal device, the downlink data from a beam B
of a second node includes: obtaining a third delay difference
between receiving, by the first node by using the beam A, an uplink
reference signal transmitted by the first terminal device and
receiving, by the second node by using the beam B, an uplink
reference signal transmitted by the first terminal device; and
predicting the first delay difference based on the third delay
difference.
Optionally, in an implementation of the first aspect, the method
further includes: controlling the first node and the second node to
simultaneously transmit correction signals in an uplink/downlink
switching guard period; obtaining a time in which the first node
receives a correction signal sent by the second node and a time in
which the second node receives a correction signal sent by the
first node; and determining a fourth delay difference between an
intermediate radio frequency channel of the first node and an
intermediate radio frequency channel of the second node based on
the time in which the first node receives the correction signal
sent by the second node and the time in which the second node
receives the correction signal sent by the first node; and
the predicting the first delay difference based on the third delay
difference includes:
predicting the first delay difference based on the third delay
difference and the fourth delay difference.
Optionally, in an implementation of the first aspect, the method
further includes: determining a second adjustment time period for
the first node based on the first adjustment time period, where the
second adjustment time period for the first node is used to adjust
a transmission time in which the first node transmits a user-level
pilot signal to the first terminal device in the first node by
using the beam A.
According to a second aspect, this application provides a wireless
communication method, used in a coordinated multipoint system that
includes a plurality of nodes, where the method includes:
obtaining, by a first node, a first adjustment time period, where
the first adjustment time period is used to adjust a transmission
time in which the first node transmits downlink data to a terminal
device by using a beam A, and the terminal device is located in a
coverage area in which the beam A of the first node intersects with
a beam B of a second node; determining, by the first node based on
the first adjustment time period, the transmission time in which
the downlink data is transmitted to the terminal device by using
the beam A; and sending, by the first node, the downlink data to
the terminal device by using the beam A based on the transmission
time.
Therefore, in this application, the first node adjusts, based on
the first adjustment time period, the transmission time in which
the downlink data is transmitted to the first terminal device by
using the beam A, to implement a beam-level signal transmission
pre-adjustment on a node side. As a result, a delay difference
between arrival, at the terminal device, of the downlink data sent
by the first node to the terminal device and arrival, at the
terminal device, of the downlink data sent by the second node to
the terminal device is less than a predetermined value.
Optionally, in an implementation of the second aspect, the
determining, by the first node based on the first adjustment time
period, the transmission time in which the downlink data is
transmitted to the terminal device by using the beam A includes:
when the first adjustment time period is greater than 0, performing
zero padding on at least two subframes for transmitting the
downlink data, where the time period on which null padding is
performed is equal to the adjustment time period; or when the first
adjustment time period is less than 0, performing null padding on a
cyclic prefix part of at least one subframe for transmitting the
downlink data, where a transmission time of a part on which null
padding is performed and that is of the cyclic prefix part of the
at least one subframe is equal to an absolute value of the
adjustment time period.
In this case, zero padding is performed on the at least two
adjacent subframes or null padding is performed on the cyclic
prefix part of the at least one subframe based on the first
adjustment time period, to achieve a timing pre-adjustment effect
on the downlink data, thereby avoiding complexity of adjusting a
physical transmission time at an OFDM symbol level.
Optionally, in an implementation of the second aspect, the method
further includes: obtaining a second adjustment time period, where
the second adjustment time period is used to adjust a transmission
time in which the first node transmits a user-level pilot signal to
the terminal device by using the beam A; determining, by the first
node based on the second adjustment time period, the transmission
time in which the user-level pilot signal is transmitted to the
first terminal device by using the beam A; and sending, by the
first node, the user-level pilot signal to the first terminal
device by using the beam A.
Optionally, in an implementation of the second aspect, when another
terminal device that performs time division multiplexing with the
terminal device is on the beam A, the determining, by the first
node based on the first adjustment time period, the transmission
time in which the downlink data is transmitted to the terminal
device by using the beam A further includes: determining, at a
moment of a switchover between the terminal device and the another
terminal device, whether there is intersymbol interference between
the terminal device and the another terminal device; and if there
is intersymbol interference between the terminal device and the
another terminal device, a time interval is reserved at the moment
of the switchover between the terminal device and the another
terminal device.
In this case, the time interval is reserved at the moment of the
switchover between the terminal device and the another terminal
device that are on the transmit beam A and that perform time
division multiplexing, thereby effectively avoiding intersymbol
interference between the terminal device and the another terminal
device.
Optionally, in an implementation of the second aspect, before the
obtaining, by a first node, a first adjustment time period, the
method further includes: determining the beam A corresponding to
the node based on beam measurement information sent by the terminal
device and/or information about whether a plurality of terminal
devices that perform time division multiplexing or frequency
division multiplexing are on a plurality of transmit beams of the
node, where the beam measurement information is used to indicate
measurement information of the plurality of transmit beams of the
node that are measured by the terminal device.
Optionally, in an implementation of the second aspect, the beam
measurement information includes at least one type of the following
information: beam spectral efficiency, a beam signal-to-noise
ratio, and a beam throughput; and
the determining the beam A corresponding to the node based on beam
measurement information sent by the terminal device and/or
information about whether a plurality of terminal devices that
perform time division multiplexing or frequency division
multiplexing are on a plurality of transmit beams of the node
includes: selecting at least one transmit beam from the plurality
of transmit beams based on the beam measurement information; and
determining the beam A from the at least one selected beam, where
no other terminal devices that perform frequency division
multiplexing with the first terminal device are on a beam A outside
the coverage area in which the terminal device is located, and the
coverage area is a coverage area in which the terminal device is
located and in which the beam A intersects with the beam B.
According to a third aspect, this application provides a wireless
communication method, used in a coordinated multipoint system that
includes a plurality of nodes, where the method includes:
determining, by a terminal device, a first delay difference between
receiving a downlink pilot signal from a beam A of a first node and
receiving the downlink pilot signal from a beam B of a second node,
where the terminal device is located in a coverage area in which
the beam A intersects with the beam B; and sending the first delay
difference to a control device, so that the control device
predicts, based on the first delay difference, a delay difference
between receiving, by the terminal device, downlink data from the
beam A of the first node and receiving, by the terminal device, the
downlink data from the beam B of the second node.
In this case, the terminal device sends, to the control device, the
first delay difference between receiving the downlink pilot signal
from the beam A of the first node and receiving the downlink pilot
signal from the beam B of the second node, so that the control
device predicts, based on the first delay difference, the delay
difference between receiving, by the terminal device, the downlink
data from the beam A of the first node and receiving, by the
terminal device, the downlink data from the beam B of the second
node.
Optionally, in an implementation of the third aspect, the
determining a first delay difference between receiving a downlink
pilot signal from a beam A of a first node and receiving the
downlink pilot signal from a beam B of a second node includes:
determining the first delay difference based on a moment at which a
cell-level pilot signal is received from the beam A of the first
node and a moment at which a cell-level pilot signal is received
from the beam B of the second node, where the first delay
difference is used by the control device to determine, in an
initial transmission phase of the downlink data, an adjustment time
period used for sending, by the first node, the downlink data to
the first terminal device.
Optionally, in an implementation of the third aspect, the
determining a first delay difference between receiving a downlink
pilot signal from a beam A of a first node and receiving the
downlink pilot signal from a beam B of a second node includes:
determining the first delay difference based on a moment at which a
user-level pilot signal is received from the beam A of the first
node and a moment at which a user-level pilot signal is received
from the beam B of the second node, where the first delay
difference is used by the control device to determine, in a
continuous transmission phase of the downlink data, an adjustment
time period used for sending, by the first node, the downlink data
to the first terminal device.
Optionally, in an implementation of the third aspect, before the
determining, by a terminal device, a first delay difference between
receiving a downlink pilot signal from a beam A of a first node and
receiving the downlink pilot signal from a beam B of a second node,
the method further includes:
sending beam measurement information of a plurality of measured
beams of the first node to the first node, and sending beam
measurement information of a plurality of measured beams of the
second node to the second node, so that the first node determines
the beam A based on the beam measurement information, and the
second node determines the beam B based on the beam measurement
information.
According to a fourth aspect, an embodiment of this application
provides a control device, including a prediction module and a
determining module, and the control device may perform the method
in the first aspect or any optional implementation of the first
aspect.
According to a fifth aspect, an embodiment of this application
provides a node, including an obtaining module, a processing
module, and a sending module, and the node may perform the method
in the second aspect or any optional implementation of the second
aspect.
According to a sixth aspect, an embodiment of this application
provides a terminal device, including a receiving module and a
determining module, and the terminal device may perform the method
in the third aspect or any optional implementation of the third
aspect.
According to a seventh aspect, a control device is provided,
including a memory, a transceiver, and a processor. The memory
stores program code that may be used to instruct to perform the
method in the first aspect or any optional implementation of the
first aspect. The transceiver is configured to receive and send a
specific signal after being driven by the processor. When the code
is executed, the processor may implement the operations performed
by the control device in the method.
According to an eighth aspect, a node is provided, including a
memory, a transceiver, and a processor. The memory stores program
code that may be used to instruct to perform the method in the
second aspect or any optional implementation of the second aspect.
The transceiver is configured to receive and send a specific signal
after being driven by the processor. When the code is executed, the
processor may implement the operations performed by the node in the
method.
According to a ninth aspect, a terminal device is provided,
including a memory, a transceiver, and a processor. The memory
stores program code that may be used to instruct to perform the
method in the third aspect or any optional implementation of the
third aspect. The transceiver is configured to receive and send a
specific signal after being driven by the processor. When the code
is executed, the processor may implement the operations performed
by the terminal device in the method.
According to a tenth aspect, a computer storage medium is provided.
The computer storage medium stores program code, and the program
code may be used to instruct to perform the method in the first
aspect or any optional implementation of the first aspect.
According to an eleventh aspect, a computer storage medium is
provided. The computer storage medium stores program code, and the
program code may be used to instruct to perform the method in the
second aspect or any optional implementation of the second
aspect.
According to a twelfth aspect, a computer storage medium is
provided. The computer storage medium stores program code, and the
program code may be used to instruct to perform the method in the
third aspect or any optional implementation of the third
aspect.
DESCRIPTION OF DRAWINGS
FIG. 1 is a schematic diagram of a communications system including
a wireless communication method, a control device, a node, and a
terminal device according to this application;
FIG. 2 is a schematic flowchart of a wireless communication method
according to this application;
FIG. 3 is a schematic diagram of transmitting a correction signal
between nodes according to this application;
FIG. 4 is a schematic diagram of an intermediate radio frequency
channel transmission delay between nodes according to this
application;
FIG. 5 is a schematic diagram of an uplink transmission delay from
a terminal device to a node according to this application;
FIG. 6 is a schematic diagram of a downlink transmission delay from
a node to a terminal device according to this application;
FIG. 7 is a schematic flowchart of a wireless communication method
according to this application;
FIG. 8 is a schematic diagram of adjusting a data transmission time
by a node according to this application;
FIG. 9 is a schematic diagram of a spatial beam grid according to
this application;
FIG. 10 is a schematic diagram of adjusting a downlink data
transmission time according to this application;
FIG. 11 is a schematic diagram of a method for activating a node in
a spatial beam grid according to this application;
FIG. 12 is a schematic diagram of an activated node in a spatial
beam grid according to this application;
FIG. 13 is a schematic flowchart of a wireless communication method
according to this application;
FIG. 14 is a schematic block diagram of a control device according
to this application;
FIG. 15 is a schematic block diagram of a node according to this
application;
FIG. 16 is a schematic block diagram of a node according to this
application;
FIG. 17 is a schematic block diagram of a terminal device according
to this application; and
FIG. 18 is a schematic block diagram of a communications device
according to this application.
DESCRIPTION OF EMBODIMENTS
The following describes technical solutions of this application
with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of a communications system including
a method, a control device, a node, and a terminal device that are
used for coordinated multipoint wireless communications according
to this application. As shown in FIG. 1, the communications system
100 includes a network device 102 and a network device 122. The
network device 102 may include a plurality of antennas such as
antennas 104, 106, 108, 110, 112, and 114. The network device 122
may include a plurality of antennas such as antennas 124, 126, 128,
130, 132, and 134. In addition, the network device 102 and the
network device 122 each may additionally include a transmitter
chain and a receiver chain. A person of ordinary skill in the art
may understand that the transmitter chain and the receiver chain
may include a plurality of components (for example, a processor, a
modulator, a multiplexer, a demodulator, a demultiplexer, or an
antenna) related to signal sending and receiving.
The network devices 102 and 122 may communicate with a plurality of
terminal devices. It may be understood that the network devices 102
and 122 may communicate with any quantity of target terminal
devices similar to a terminal device 116.
As shown in FIG. 1, the terminal device 116 communicates with the
antennas 112 and 114. The antennas 112 and 114 send information to
the terminal device 116 over a forward link 118, and receive
information from the terminal device 116 over a reverse link 120.
In addition, the terminal device 116 communicates with the antennas
124 and 126. The antennas 124 and 126 send information to the
terminal device 116 over a forward link 136, and receive
information from the terminal device 116 over a reverse link
138.
Within a given time, the network device 102, the network device
122, or the terminal device 116 may be a wireless communications
sending apparatus and/or a wireless communications receiving
apparatus. When sending data, the wireless communications sending
apparatus may encode the data for transmission. Specifically, the
wireless communications sending apparatus may obtain (for example,
generate, receive from another communications apparatus, or store
in a memory) a specific quantity of target data bits that need to
be sent to the wireless communications receiving apparatus through
a channel. The data bits may be included in a data transport block
(or a plurality of transport blocks), and the transport block may
be segmented to generate a plurality of code blocks.
In addition, the communications system 100 may be a public land
mobile network (PLMN) or another network. FIG. 1 is merely a
simplified schematic diagram of an example. The network may further
include another network device that is not shown in FIG. 1.
Optionally, in the embodiments of this application, the network
device may be a device that communicates with a terminal device,
for example, a base station or a base station controller. Each
network device may provide communication coverage for a specific
geographical area, and may communicate with a terminal device (for
example, UE) located in the coverage area. The network device may
support communications protocols of different standards, or may
support different communication modes. For example, the network
device may be a base transceiver station (BTS) in a global system
for mobile communications (GSM) or a code division multiple access
(CDMA) system, a NodeB (NB) in a wideband code division multiple
access system, an evolved NodeB (eNB or eNodeB) in a long term
evolution system, or a radio controller in a cloud radio access
network (CRAN). Alternatively, the network device may be a network
device in a future 5G network, a network device in a future evolved
public land mobile network (PLMN), or the like.
Optionally, in the embodiments of this application, the terminal
device may be an access terminal, a terminal device (User
Equipment, UE), a terminal unit, a terminal station, a mobile
station, a mobile console, a remote station, a remote terminal, a
mobile terminal, a terminal, a wireless communications device, a
terminal agent, or a terminal apparatus. The access terminal may be
a cellular phone, a cordless phone, a session initiation protocol
(SIP) phone, a wireless local loop (WLL) station, a personal
digital assistant (PDA), a handheld device having a wireless
communications function, a computing device, another processing
device connected to a wireless modem, an in-vehicle device, a
wearable device, a terminal device in internet of things, a virtual
reality device, a terminal device in the future 5G network, a
terminal device in the future evolved public land mobile network
(PLMN), or the like.
The wireless communication method and the device provided in the
embodiments of this application may be applied to a terminal
device. The terminal includes a hardware layer, an operating system
layer running above the hardware layer, and an application layer
running above the operating system layer. The hardware layer
includes hardware such as a central processing unit (CPU), a memory
management unit (MMU), and a memory (also referred to as a main
memory). The operating system may be any one or more computer
operating systems that process a service by using a process, for
example, a Linux operating system, a Unix operating system, an
Android operating system, an iOS operating system, or a Windows
operating system. The application layer includes applications such
as a browser, an address book, word processing software, and
instant messaging software.
In addition, aspects or features of this application may be
implemented as a method, an apparatus or a product that uses
standard programming and/or engineering technologies. The term
"product" used in this application covers a computer program that
can be accessed from any computer-readable component, carrier or
medium. For example, the computer-readable medium may include but
is not limited to a magnetic storage device (for example, a hard
disk, a floppy disk, or a magnetic tape), an optical disc (for
example, a compact disc (CD), a digital versatile disc (DVD)), a
smart card, and a flash storage device (for example, an erasable
programmable read-only memory (EPROM), a card, a stick, or a key
drive)). In addition, various storage media described in this
specification may indicate one or more devices and/or other
machine-readable media that are configured to store information.
The term "machine-readable media" may include but are not limited
to various media that can store, contain and/or carry an
instruction and/or data.
To better understand this application, this application is
described below with reference to FIG. 2 to FIG. 18 by using a
system the same as or similar to the system shown in FIG. 1 as an
example.
FIG. 2 is a schematic flowchart of a wireless communication method
200 according to this application. The method is used in a
coordinated multipoint system that includes a plurality of nodes.
As shown in FIG. 2, the method 200 includes the following
content.
Step 210: Predict a first delay difference between receiving, by a
terminal device, downlink data from a beam A of a first node and
receiving, by the terminal device, the downlink data from a beam B
of a second node, where the terminal device is located in a
coverage area in which the beam A intersects with the beam B.
Optionally, the predicting a first delay difference between
receiving, by a terminal device, downlink data from a beam A of a
first node and receiving, by the terminal device, the downlink data
from a beam B of a second node includes: obtaining a second delay
difference between receiving, by the terminal device, a downlink
pilot signal from the beam A of the first node and receiving, by
the terminal device, a downlink pilot signal from the beam B of the
second node; and predicting the first delay difference based on the
second delay difference.
Specifically, the terminal device determines, based on a time of
receiving the downlink pilot signal from the beam A of the first
node and a time of receiving the downlink pilot signal from the
beam B of the second node, the second delay difference between
receiving, by the terminal device, the downlink pilot signal from
the beam A of the first node and receiving, by the terminal device,
the downlink pilot signal from the beam B of the second node, and
the first terminal device sends the second delay difference to a
control device. The control device estimates the first delay
difference based on the second delay difference.
The terminal device uses the second node as a reference node, and
the terminal device calculates a difference between the time of
receiving the downlink pilot signal from the beam A of the first
node and the time of receiving the downlink pilot signal from the
beam B of the second node, and determines the difference as the
second delay difference.
It should be understood that the terminal device may send, to the
control device, the time of receiving, by the terminal device, the
downlink pilot signal from the beam A of the first node and the
time of receiving, by the terminal device, the downlink pilot
signal from the beam B of the second node. The control device
determines, based on the receiving times sent by the first terminal
device, the second delay difference between receiving, by the
terminal device, the downlink pilot signal from the beam A of the
first node and receiving, by the terminal device, the downlink
pilot signal from the beam B of the second node, and the control
device estimates the first delay difference based on the second
delay difference.
It should be further understood that the control device may be
either the first node or the second node. A primary node and a
secondary node are determined in the first node and the second
node. In addition to sending a signal to the terminal device, the
primary node is further configured to control the plurality of
nodes to adjust a downlink data transmission time.
Optionally, the predicting, by a control device, a first delay
difference between receiving, by a terminal device, downlink data
from a beam A of a first node and receiving, by the terminal
device, the downlink data from a beam B of a second node includes:
when a plurality of first terminal devices that perform frequency
division multiplexing are in the coverage area in which the
terminal device is located and in which the beam A of the first
node intersects with the beam B of the second node, obtaining
second delay differences of the plurality of first terminal devices
that perform frequency division multiplexing, and estimating the
first delay difference based on an average value of the second
delay differences.
Specifically, at a high frequency and in a massive antenna array,
terminal devices that belong to a same beam node and that perform
frequency division multiplexing are similar in spatial locations,
and inter-TP air interface transmission delay features and inter-TP
delay differences (including IRF timing errors) of the terminal
devices are also similar. Therefore, the first delay difference may
be estimated based on an average value of the inter-TP delay
differences fed back by the terminal devices.
Optionally, the obtaining a second delay difference between
receiving, by the terminal device, a downlink pilot signal from the
beam A of the first node and receiving, by the terminal device, a
downlink pilot signal from the beam B of the second node includes:
obtaining the second delay difference between sending, by the
terminal device, the downlink pilot signal to the terminal device
on a first path of the beam A of the first node and sending, by the
second node, the downlink pilot signal to the terminal device on a
first path of the beam B. The first path is usually a line of sight
(LOS) path. When there is no line of sight path on the beam A, the
first path is a non-line of sight (NLOS) path with a shortest
transmission distance.
Optionally, before the first node transmits the downlink data to
the terminal device by using the beam A and the second node
transmits the downlink data to the terminal device by using the
beam B, the downlink pilot signal is a cell-level pilot signal.
Specifically, when the first terminal device receives a cell-level
pilot signal from the first node and a cell-level pilot signal from
the second node, for example, the cell-level pilot signals are
synchronization shift (SS) signals, the first terminal device
determines the second delay difference based on pilot signals,
namely, SSs, from the first node and the second node, and the first
terminal device sends the second delay difference to the control
device. The control device receives the second delay difference
sent by the first terminal device, and predicts, based on the
second delay difference, the first delay difference between
receiving, by the terminal device, the downlink data from the beam
A of the first node and receiving, by the terminal device, the
downlink data from the beam B of the second node. The first delay
difference is used as a timing adjustment to an initial state of
the transmitted downlink data.
In this case, the first delay difference is determined based on the
second delay difference between receiving, by the terminal device,
the cell-level pilot signal from the beam A of the first node and
receiving, by the terminal device, the cell-level pilot signal from
the beam B of the second node. Therefore, before the downlink data
is transmitted, a first adjustment time period used for sending, by
the first node, the downlink data to the first terminal device is
determined based on the first delay difference, so that a delay
difference between receiving, by the terminal device, the downlink
data from the beam A and receiving, by the terminal device, the
downlink data from the beam B is less than a predetermined value.
Optionally, in an implementation of the first aspect, when the
first node transmits the downlink data to the terminal device by
using the beam A and the second node transmits the downlink data to
the terminal device by using the beam B, the downlink pilot signal
is a user-level pilot signal.
Specifically, when the first terminal device receives a user-level
pilot signal from the first node and a user-level pilot signal from
the second node, for example, the user-level pilot signal is a
measurement pilot (channel state indication reference signal, CSI),
the first terminal device determines the second delay difference
based on measurement pilot signals, namely, CSIs, from the
plurality of nodes, and the first terminal device sends the second
delay difference to the control device. The control device receives
the second delay difference sent by the first terminal device, and
predicts, based on the second delay difference, the first delay
difference between receiving, by the terminal device, the downlink
data from the beam A of the first node and receiving, by the
terminal device, the downlink data from the beam B of the second
node. The first delay difference is used as a timing adjustment to
a tracking state of the downlink data.
In this case, the first delay difference is determined based on the
second delay difference between receiving, by the terminal device,
the user-level pilot signal from the beam A of the first node and
receiving, by the terminal device, the user-level pilot signal from
the beam B of the second node. Therefore, when the downlink data is
transmitted, a first adjustment time period used for sending, by
the first node, the downlink data to the first terminal device is
determined based on the first delay difference, so that a delay
difference between receiving, by the terminal device, the downlink
data from the beam A and receiving, by the terminal device, the
downlink data from the beam B is less than a predetermined
value.
Optionally, the cell-level pilot signal or the user-level pilot
signal or both are decoupled, and time division transmission may be
performed on the cell-level pilot signal and/or the user-level
pilot signal by using different subframes.
Specifically, the cell-level pilot signal is a common reference
signal of all terminal devices in a cell, and the control device
needs to estimate first delay differences of all the terminal
devices in the cell in an initial transmission phase of the
downlink data based on the cell-level pilot signal. Therefore, a
timing pre-adjustment at a transmit end is not suitable for the
cell-level pilot signal, to be specific, the cell-level pilot
signal needs to be decoupled from the user-level pilot signal, to
ensure that a timing pre-adjustment to the user-level pilot signal
does not affect transmission of the cell-level pilot signal. For
example, time division transmission is performed on the cell-level
pilot signal and the user-level pilot signal by using different
subframes, the cell-level pilot signals are transmitted in a single
subframe together, and no data signal is transmitted in the
cell-level pilot subframe.
Optionally, the predicting a first delay difference between
receiving, by a terminal device, downlink data from a beam A of a
first node and receiving, by the terminal device, the downlink data
from a beam B of a second node includes: obtaining a third delay
difference between receiving, by the first node by using the beam
A, an uplink reference signal transmitted by the first terminal
device and receiving, by the second node by using the beam B, an
uplink reference signal transmitted by the first terminal device;
and predicting the first delay difference based on the third delay
difference.
Specifically, when receiving an uplink pilot signal sent by the
first terminal device, for example, the uplink pilot signal is an
uplink reference signal (Sounding Reference Signals, SRS), the
first node and the second node send moments at which the uplink
pilot signal, namely, the SRS, is received to the control device.
The control device receives the moments at which the uplink pilot
signal, namely, the SRS, is received and that are sent by the first
node and the second node; calculates, by using the second node as a
reference node, a difference between times of receiving the uplink
pilot signal, namely, the SRS, by the first node and the second
node, where the time difference is the third delay difference; and
estimates the first delay difference based on the third delay
difference.
Optionally, the method further includes: controlling the first node
and the second node to simultaneously transmit correction signals
in an uplink/downlink switching guard period; obtaining a time in
which the first node receives a correction signal sent by the
second node and a time in which the second node receives a
correction signal sent by the first node; and determining a fourth
delay difference between an intermediate radio frequency channel of
the first node and an intermediate radio frequency channel of the
second node based on the time in which the first node receives the
correction signal sent by the second node and the time in which the
second node receives the correction signal sent by the first node;
and
the predicting the first delay difference based on the third delay
difference includes:
predicting the first delay difference based on the third delay
difference and the fourth delay difference.
Specifically, transmission delays of a node include an IRF
intermediate radio frequency channel delay and an air interface
transmission delay. The control device separately estimates IRF
intermediate radio frequency channel delays and uplink air
interface transmission delays of the first node and the second
node, and estimates, based on the IRF intermediate radio frequency
channel delays and the uplink air interface transmission delays, a
delay of transmitting, by the first node, the downlink data to the
first terminal device by using a first transmit beam of the first
node and a delay of transmitting, by the second node, the downlink
data to the first terminal device by using a first transmit beam of
the second node. First, the control device estimates an
uplink/downlink IRF channel delay difference between the first node
and the second node by using correction signals between the first
node and the second node. For example, the first node and the
second node transmit correction signals in a time division
duplexing (TDD) uplink/downlink switching guard period (GP), and
the correction signal is in a form of an orthogonal sequence to
reduce mutual interference. Each coordinated TP selects an
orthogonal sequence corresponding to a target signal from received
correction signals, and estimates a first path delay difference
between the first node and the second node by using a method such
as correlation peak detection and multi-frame filtering. The
control device estimates the uplink/downlink IRF channel delay
difference between the first node and the second node based on the
first path delay difference between the first node and the second
node. Second, the control device determines an uplink transmission
delay difference between the first node and the second node based
on the uplink transmission delay difference between receiving, by
the first node, the uplink reference signal sent by the first
terminal device and receiving, by the second node, the uplink
reference signal sent by the first terminal device. Third, a
downlink transmission delay difference between the first node and
the second node is determined based on the IRF channel delay and
the inter-TP uplink transmission delay difference between the first
node and the second node.
For example, in FIG. 3, a node TP 0 and a node TP 1 are coordinated
nodes. The node TP 0 is a primary node, and may function as the
control device. The node TP 0 and the node TP 1 transmit correction
signals in a TDD uplink/downlink switching guard period (GP). The
node TP 0 receives a correction signal transmitted by the node TP 0
and a correction signal transmitted by the node TP 1. The node TP 0
determines an orthogonal sequence corresponding to a target signal
(which is referred to as the correction signal from the node 1
herein) from the received correction signals. As shown in FIG. 4,
the node TP 0 and the node TP 1 send correction signals to each
other in a TDD uplink/downlink switching GP period. The TP 0
selects, from received correction signals, an orthogonal sequence
corresponding to a target signal sent by the TP 1, and estimates a
first path delay difference between the TPs by using a method such
as correlation peak detection and multi-frame filtering. The TP 1
selects, from received correction signals, an orthogonal sequence
corresponding to a target signal sent by the TP 0, estimates a
first path delay difference between the TPs by using a method such
as correlation peak detection and multi-frame filtering, and sends
the first path transmission delay to the TP 0. Because the first
path transmission delays are equal, the TP 0 estimates an
uplink/downlink IRF channel delay difference between the TP 0 and
the TP 1 based on the first path delay.
FIG. 5 shows an uplink transmission delay difference between the TP
0 and the TP 1 in receiving the uplink reference signal sent by the
first terminal device. The TP 1 sends, to the TP 0, the uplink
transmission delay in receiving the uplink reference signal sent by
the first terminal device.
FIG. 6 shows a transmission delay difference between the TP 0 and
the TP1 in sending downlink data to the first terminal device. The
TP 0 estimates, based on the uplink/downlink IRF channel delay
difference between the TP 0 and the TP 1 and the uplink
transmission delay difference between the TP 0 and the TP 1 in
receiving the uplink reference signal sent by the first terminal
device, the downlink transmission delay difference between the TP 0
and the TP 1 in sending the downlink data to the first terminal
device.
It should be understood that the node TP 0 and the node TP 1 are
merely examples, and constitute no limitation on this application.
An intermediate radio frequency channel delay difference between a
plurality of nodes and a transmission delay difference between the
plurality of nodes may also be determined according to a similar
method.
Step 220: Determine a first adjustment time period based on the
first delay difference, where the first adjustment time period is
used to adjust a transmission time in which the first node
transmits the downlink data to the terminal device by using the
beam A, so that a delay difference between receiving, by the
terminal device, the downlink data from the beam A and receiving,
by the terminal device, the downlink data from the beam B is less
than a predetermined value.
Optionally, the control device sends the first adjustment time
period to the first node, so that the first node sends the downlink
data to the first terminal device by using the beam A based on the
first adjustment time period.
Optionally, when the control device is the first node, the control
device may send the downlink data to the first terminal device by
using the beam A based on the first adjustment time period. When
the first adjustment time period is greater than 0, zero padding is
performed on at least two subframes for transmitting the downlink
data, where the time period on which null padding is performed is
equal to the first adjustment time period. Alternatively, when the
first adjustment time period is less than 0, null padding is
performed on a cyclic prefix part of at least one subframe for
transmitting the downlink data, where a transmission time of a part
on which null padding is performed and that is of the cyclic prefix
part of the at least one subframe is equal to an absolute value of
the adjustment time period.
It should be understood that in this embodiment of this
application, there may be a plurality of first nodes, and the
second node is a reference node. The first node is merely used as
an example, and constitutes no limitation on this application.
Therefore, in this embodiment of this application, the first delay
difference between receiving, by the terminal device, the downlink
data from the beam A of the first node and receiving, by the
terminal device, the downlink data from the beam B of the second
node is predicted, and the transmission time in which the first
node sends the downlink data to the terminal device by using the
beam A is determined based on the first delay difference, to
implement a beam-level signal transmission pre-adjustment on a node
side. As a result, a delay difference between arrival, at the first
terminal device, of the downlink data sent by the first node to the
first terminal device and arrival, at the first terminal device, of
the downlink data sent by the second node to the first terminal
device is less than the predetermined value. This resolves an ISI
interference problem and a coordinated area shrinkage problem that
are introduced due to an inter-TP air interface transmission delay
difference and an inter-TP IRF timing error in a coordinated
technology, thereby effectively increasing a coordinated area and a
coordinated gain particularly in a scenario of a shorter CP in a 5G
high-frequency system.
FIG. 7 is a schematic flowchart of a wireless communication method
300 according to this application. The method 300 is used in a
coordinated multipoint system that includes a plurality of nodes.
As shown in FIG. 7, the method 300 includes the following
content.
Step 310: A first node obtains a first adjustment time period,
where the first adjustment time period is used to adjust a
transmission time in which the first node transmits downlink data
to a terminal device by using a beam A, and the terminal device is
located in a coverage area in which the beam A of the first node
intersects with a beam B of a second node.
Step 320: The first node determines, based on the first adjustment
time period, the transmission time in which the downlink data is
transmitted to the terminal device by using the beam A.
Optionally, that the first node determines, based on the first
adjustment time period, the transmission time in which the downlink
data is transmitted to the first terminal device by using the beam
A includes: when the first adjustment time period is greater than
0, performing zero padding on at least two subframes for
transmitting the downlink data, where the time period on which null
padding is performed is equal to the adjustment time period; or
when the first adjustment time period is less than 0, performing
null padding on a cyclic prefix part of at least one subframe for
transmitting the downlink data, where a transmission time of a part
on which null padding is performed and that is of the cyclic prefix
part of the at least one subframe is equal to an absolute value of
the adjustment time period.
Specifically, the node receives the first adjustment time period
sent by the control device, and adjusts a transmit signal on the
beam A based on the first adjustment time period. In principle,
this may be implemented by adjusting a physical transmission time
of an OFDM-symbol-level signal. However, the method is relatively
complex, and typically, a signal is usually transmitted on an IRF
interface on a frame basis. One radio frame includes 10 subframes
and 20 timeslots, and each downlink timeslot is further divided
into several OFDM symbols. A quantity of included OFDM symbols
varies with a CP length. When a normal CP is used, one downlink
timeslot includes seven OFDM symbols. When an extended CP is used,
one downlink timeslot includes six OFDM symbols. To match an
existing IRF interface, a framing method on a baseband side is
shown in FIG. 8. It may be learned from FIG. 8 that a subframe with
a timing pre-adjustment effect may be formed by partially
concatenating two original adjacent subframe (or radio frame)
signals. When the first adjustment time period
.DELTA..sub..DELTA..sub.d received by the node is greater than 0,
the time in which the node sends the downlink data is delayed by
the first adjustment time period, and zero padding may be performed
on two adjacent subframes, where a time period on which zero
padding is performed is equal to the first adjustment time period.
As shown in FIG. 8, when the first adjustment time period
.DELTA..sub..DELTA.d received by the node is greater than 0, zero
padding is performed after the first subframe. When the first
adjustment time period .DELTA..sub..DELTA..sub.d received by the
node is less than 0, the time in which the node sends the downlink
data is advanced by the first adjustment time period, and null
padding may be performed on a part of a cyclic prefix part of at
least one subframe for transmitting the downlink data, where a
transmission time of the part that is of the cyclic prefix part of
the at least one subframe and on which null padding is performed is
equal to an absolute value of the adjustment time period. As shown
in FIG. 8, when the first adjustment time period
.DELTA..sub..DELTA..sub.d received by the node is less than 0, null
padding is not performed on a CP part of the second subframe.
In this case, zero padding is performed on the at least two
adjacent subframes or null padding is performed on the cyclic
prefix part of the at least one subframe based on the first
adjustment time period, to achieve a timing pre-adjustment effect
on the downlink data, thereby avoiding complexity of adjusting a
physical transmission time at an OFDM symbol level.
Optionally, when another terminal device that performs time
division multiplexing with the terminal device is on the beam A,
that the first node determines, based on the first adjustment time
period, the transmission time in which the downlink data is
transmitted to the terminal device by using the beam A further
includes: determining, at a moment of a switchover between the
terminal device and the another terminal device, whether there is
intersymbol interference between the terminal device and the
another terminal device; and if there is intersymbol interference
between the terminal device and the another terminal device, a time
interval is reserved at the moment of the switchover between the
terminal device and the another terminal device.
Specifically, when a plurality of terminal devices that perform
time division multiplexing are on the beam A, the plurality of
terminal devices that perform time division multiplexing may
perform time division multiplexing on one node using the beam A, or
may perform time division multiplexing on different nodes using the
beam A. At a transmit moment switching point of each two of the
plurality of terminal devices that perform time division
multiplexing, intersymbol interference in two adjacent
transmissions is determined based on a positive or negative value
of a first delay difference between the two terminal devices. If
there is intersymbol interference, the node reserves a specific
interval at a moment of a switchover between the two terminal
devices, for example, reserves one reserved time interval TTI.
In this case, the time interval is reserved at the moment of the
switchover between the terminal device and the another terminal
device that are on the transmit beam A and that perform time
division multiplexing, thereby effectively avoiding intersymbol
interference between the terminal device and the another terminal
device.
Optionally, the method further includes: obtaining a second
adjustment time period, where the second adjustment time period is
used to adjust a transmission time in which the first node
transmits a user-level pilot signal to the terminal device by using
the beam A; determining, by the first node based on the second
adjustment time period, the transmission time in which the
user-level pilot signal is transmitted to the terminal device by
using the beam A; and sending, by the first node, the user-level
pilot signal to the terminal device by using the beam A.
Specifically, in a continuous transmission phase of the data, the
first node adjusts the transmission time of the downlink data based
on the first adjustment time period. Because the user-level pilot
signal is sent at a time interval of sending the downlink data, the
user-level pilot signal from the node is also adjusted based on the
first adjustment time period.
Optionally, before the first node obtains the first adjustment time
period, the method further includes: determining the beam A
corresponding to the node based on beam measurement information
sent by the terminal device and/or information about whether a
plurality of terminal devices that perform time division
multiplexing or frequency division multiplexing are on a plurality
of transmit beams of the node, where the beam measurement
information is used to indicate measurement information of the
plurality of transmit beams of the node that are measured by the
terminal device.
Optionally, the beam measurement information includes at least one
type of the following information: beam spectral efficiency, a beam
signal-to-noise ratio, and a beam throughput. The determining the
beam A corresponding to the node based on beam measurement
information sent by the first terminal device and/or information
about whether a plurality of terminal devices that perform time
division multiplexing or frequency division multiplexing are on a
plurality of transmit beams of the node includes: selecting at
least one transmit beam from the plurality of transmit beams based
on the beam measurement information; and determining the beam A
from the at least one selected beam. No other terminal devices that
perform frequency division multiplexing with the terminal device
are on a beam A outside the coverage area in which the terminal
device is located, and the coverage area is a coverage area in
which the first terminal device is located and in which the beam A
intersects with the beam B.
Specifically, for a massive array antenna of a plurality of nodes,
a plurality of beams with relatively good orthogonality or spatial
isolation (which may be physically represented as specific forms
such as adaptive beamforming ABF beams or subarrays) are formed by
using a technology such as static weighting or ABF, and the
plurality of beams are spatially interleaved to form a beam grid
node Lattice. The first terminal device scans and measures beams of
a plurality of coordinated TPs, to obtain an optimal beam of each
TP, where the optimal beam is used as a first transmit beam. A node
at which the first transmit beams of the plurality of coordinated
TPs intersect is a node of the terminal in the beam grid.
For example, in FIG. 9, beams of a node TP 0 and a node TP 1 form a
spatial beam grid. The beams of the node TP 0 are a beam 0 of the
TP 0, a beam 1 of the TP 0, and a beam 2 of the TP 0, and the beams
of the node TP 1 are a beam 0 of the TP 1, a beam 1 of the TP 1,
and a beam 2 of the TP 1. The beams of the TP 0 and the TP 1 are
interleaved to form the spatial beam grid, a quantity of nodes
formed by using the TP 0 and the TP 1 is 9, and (m,n) is defined as
a node formed by an m.sup.th beam of the TP 0 and an n.sup.th beam
of the TP 1 through interleaving. For a k.sup.th terminal, a home
lattice node of the k.sup.th terminal and a measured value of
coordinated spectral efficiency, marked as c.sub.m,n,k, of the
k.sup.th terminal may be obtained by scanning and measuring beams
of coordinated TPs on a downlink receiving side.
A method for measuring the coordinated spectral efficiency
c.sub.m,n,k, depends on a specific coordinated solution and a
measurement and feedback method. Several example methods are as
follows:
Method 1: The k.sup.th terminal device measures and reflects a
spectral efficiency estimation value, marked as c.sub.0,m,k, (which
may be converted by using a signal CQI or the like) of the m.sup.th
beam of the TP0, and selects a largest value c.sub.0,m,k from a set
{C.sub.0,m,k}.sub.m measured values of the beams of the TP 0, and
similarly, the k.sup.th terminal device measures and reflects a
spectral efficiency estimation value c.sub.1,n,k of the n.sup.th
beam of the TP 1, and selects a largest value c.sub.1,n,k from a
set {c.sub.1,n,k}.sub.n of measured values of the beams of the TP
1, to determine the home beam lattice node ({tilde over (m)},n) and
the spectral efficiency c.sub.{tilde over (m)},n,{tilde over
(k)}=c.sub.0,{tilde over (m)},k+c.sub.1,n,k that are corresponding
to the terminal device. It should be noted that the spectral
efficiency estimation method cannot reflect impact of mutual
interference between beams.
Method 2: The k.sup.th terminal device performs joint measurement
on the m.sup.th beam of the TP 0 and the n.sup.th beam of the TP 1,
to obtain overall spectral efficiency c.sub.m,n,k under a condition
that mutual interference between beams can be sensed, and selects a
largest value c.sub.{tilde over (m)},n,{tilde over (k)} from a set
{c.sub.m,n,k}.sub.m,n, to determine the home beam lattice node
corresponding to the terminal.
For a specific lattice node (m,n), there may be a plurality of
terminal devices. From a perspective of maximum spectral
efficiency, a terminal with the maximum spectral efficiency is
selected as the first terminal device from a set
{C.sub.m,n,k}.sub.k.
It may be learned from FIG. 9 that a one-dimensional overlapping
degree or a two-dimensional overlapping degree of a node in the
grid that is selected based on a coordinated spectral efficiency
measured by the terminal device may be greater than 0. That a
one-dimensional overlapping degree is greater than 0 means that
there are a plurality of worker nodes using a beam used by a node
in the spatial beam grid, and that a two-dimensional overlapping
degree is greater than 0 means that there are a plurality of worker
nodes using two beams that intersect at a node in the spatial beam
grid. As shown in FIG. 9, a one-dimensional overlapping degree of
the first node using the beam 1 of the TP 0 is greater than 0, and
a two-dimensional overlapping degree of the second node using the
beam 1 of the TP 0 is greater than 0. If no timing pre-adjustment
is made to the node TP 0, and orthogonality between beams is
relatively good, nodes in each spatial beam grid independently
perform coordinated transmission, in other words, overlapping
between the nodes in the spatial beam grid does not affect another
terminal device. However, if a timing pre-adjustment is made to the
node TP 0, the timing pre-adjustment affects all terminal devices
that perform multiplexing on the node TP 0. Different air interface
transmission delay differences are introduced because different
terminal devices in different nodes using a same beam have
different spatial locations. Air interface transmission delay
timing adjustment values are usually different because terminal
devices in each node have different locations. Therefore, an
adjustment of a timing adjustment to the beam 1 of the TP 0 causes
an error on a different node using the beam 1 of the TP 0. In
addition, the first node using the beam 1 of the TP 0 is located at
an intersecting point of the beam 1 of the TP 0 and the beam 0 of
the TP 1, and the second node using the beam 1 of the TP 0 is
located at an intersecting point of the beam 1 of the TP 0 and the
beam 1 of the TP 1. Therefore, the beam 1 of the TP 0 has two
adjustment values: an adjustment value for the beam 0 of the TP 1
and an adjustment value for the beam 1 of the TP 1.
As shown in FIG. 10, there is a relatively large distance between
spatial locations of two nodes using the beam 1 of the TP 0, and an
adjustment time .DELTA.1 is not equal to .DELTA.2. If a timing
pre-adjustment is made to downlink data from a terminal device in
the first node using the beam 1 of the TP 0 based on the adjustment
time .DELTA.1, receiving downlink data from a terminal device in
the second node is affected. Similarly, there is a relatively large
distance between spatial locations of two nodes using the beam 1 of
the TP 1, and an adjustment time .DELTA.3 is not equal to .DELTA.4.
If a timing pre-adjustment is made to downlink data from a terminal
device in the first node using the beam 1 of the TP 1 based on the
adjustment time .DELTA.3, receiving downlink data from a terminal
device in the second node is affected. Therefore, the nodes in the
spatial beam grid need to be independent to some extent.
With reference to the foregoing condition, the nodes in the spatial
beam grid formed by the beams of the TP 0 and the TP 1 are defined
as a matrix A.
A constraint condition and a physical meaning of the matrix A are
as follows:
(1) A value of any element is 0 or 1, and this is corresponding to
an activated or inactivated node.
(2) A two-dimensional overlapping degree b.sub.m,n of any element
or node, needs to be equal to 0, to be specific, for any node, a
row vector or a column vector in which the node is located cannot
simultaneously include a plurality of activated nodes, to ensure
two-dimensional decoupling or independence between nodes.
Generally, terminal devices in nodes in a same row or column need
to perform frequency division multiplexing or time division
multiplexing. From a perspective of maximum spectral efficiency at
a TTI level, a single node with the maximum spectral efficiency is
usually selected for data transmission. To be specific, to activate
the matrix A, a constraint that any row vector or column vector
includes only one non-zero element needs to be met. It should be
noted that the condition is not required for coordination and a
timing pre-adjustment at a transmit end, but is required based on a
feature of a beam multiplexing MIMO transmission scheme, and also
needs to be met for a single cell.
In this embodiment of this application, a method for activating the
node in the spatial beam grid formed by the coordinated TPs is
provided. In the method, on a beam, a node in which a terminal
device with maximum spectral efficiency is located is selected for
activation, extension is performed in a cross manner by using the
node as an origin, to determine other nodes associated with the
node, and these nodes are kept empty, to ensure that any two
activated nodes do not overlap, so that beam-level transmission
timing pre-adjustments are mutually decoupled, and may be
separately made.
FIG. 11 shows steps of the method. In FIG. 11, a white circle
indicates that spectral efficiency of the node is greater than
spectral efficiency of a node indicated by a circle filled with
slashes. A node (0, 1) with maximum spectral efficiency is first
activated, two nodes adjacent to the node (0, 1) are inactivated. A
node (1, 0) corresponding to a diagonal of the node (0, 1) may be
activated, and a node adjacent to the node (1, 0) is
inactivated.
FIG. 12 shows an effect of the method. It may be learned from FIG.
12 that any activated nodes do not overlap, so that beam-level
transmission timing pre-adjustments are mutually decoupled, and may
be separately made. There is only one terminal device in the
activated node, and a beam-level transmission timing pre-adjustment
may be made to the terminal device.
It should be understood that the lattice model, the constraint
condition, the lattice pre-allocation, and the spectral efficiency
maximization criterion provided in the method are merely used as
examples, and the node in the spatial beam grid may be
alternatively activated with reference to a scheduling criterion
such as a PF.
It should also be understood that the transmit beam B of the second
node may also be determined according to the method for determining
the transmit beam A by the first node. The first node and the
second node may be nodes of a same type.
Step 330: The first node sends the downlink data to the terminal
device by using the beam A based on the transmission time.
Therefore, in this embodiment of this application, the first node
adjusts, based on the first adjustment time period, the
transmission time in which the downlink data is transmitted to the
terminal device by using the beam A, to implement a beam-level
signal transmission pre-adjustment on a node side. As a result, a
delay difference between arrival, at the terminal device, of the
downlink data sent by the first node to the terminal device and
arrival, at the terminal device, of the downlink data sent by the
second node to the terminal device is less than the predetermined
value.
FIG. 13 is a schematic flowchart of a wireless communication method
400 according to this application. The method 400 is used in a
coordinated multipoint system that includes a plurality of nodes.
As shown in FIG. 13, the method 400 includes the following
content.
Step 410: A terminal device determines a first delay difference
between receiving a downlink pilot signal from a beam A of a first
node and receiving the downlink pilot signal from a beam B of a
second node, where the terminal device is located in a coverage
area in which the beam A intersects with the beam B.
Step 420: Send the first delay difference to a control device, so
that the control device predicts, based on the first delay
difference, a delay difference between receiving, by the terminal
device, downlink data from the beam A of the first node and
receiving, by the terminal device, the downlink data from the beam
B of the second node.
Therefore, in this embodiment of this application, the terminal
device sends, to the control device, the first delay difference
between receiving the downlink pilot signal from the beam A of the
first node and receiving the downlink pilot signal from the beam B
of the second node. The control device predicts, based on the first
delay difference, the first delay difference between receiving, by
the terminal device, the downlink data from the beam A of the first
node and receiving, by the terminal device, the downlink data from
the beam B of the second node, further determines a first
adjustment time period for the first node, and controls the first
node to send the downlink data to the terminal device by using the
beam A based on the first adjustment time period, to implement a
beam-level transmission pre-adjustment on a node side. As a result,
a delay difference between arrival, at the terminal device, of the
downlink data sent by the first node to the terminal device and
arrival, at the terminal device, of the downlink data sent by the
second node to the terminal device is less than a predetermined
value. This resolves an ISI interference problem and a coordinated
area shrinkage problem that are introduced due to an inter-TP air
interface transmission delay difference and an inter-TP IRF timing
error in a coordinated technology, thereby effectively increasing a
coordinated area and a coordinated gain particularly in a scenario
of a shorter CP in a 5G high-frequency system.
FIG. 14 is a schematic block diagram of a control device 500
according to an embodiment of this application. As shown in FIG.
14, the control device 500 includes:
a prediction module 510, configured to predict a first delay
difference between receiving, by a terminal device, downlink data
from a beam A of a first node and receiving, by the terminal
device, the downlink data from a beam B of a second node, where the
terminal device is located in a coverage area in which the beam A
intersects with the beam B; and
a determining module 520, configured to determine a first
adjustment time period based on the first delay difference, where
the first adjustment time period is used to adjust a transmission
time in which the first node transmits the downlink data to the
terminal device by using the beam A, so that a delay difference
between receiving, by the terminal device, the downlink data from
the beam A and receiving, by the terminal device, the downlink data
from the beam B is less than a predetermined value.
Optionally, the prediction module 510 and the determining module
520 are configured to perform operations of the wireless
communication method 200 in the embodiments of this application.
For brevity, details are not described herein again.
Optionally, as shown in FIG. 15, the control device 500 may be a
node 500. When the control device 500 is the node 500, a processing
module of the node 500 is further configured to determine, based on
the first adjustment time period, the transmission time in which
the downlink data is transmitted to the terminal device by using
the beam A. The node further includes a sending module 530,
configured to send the downlink data based on the transmission time
in which the downlink data is transmitted to the terminal device by
using the beam A.
FIG. 16 is a schematic block diagram of a node 600 according to an
embodiment of this application. As shown in FIG. 16, the node 600
includes:
an obtaining module 610, configured to obtain a first adjustment
time period, where the first adjustment time period is used to
adjust a transmission time in which the first node transmits
downlink data to a first terminal device by using a beam A, and the
terminal device is located in a coverage area in which the beam A
of the first node intersects with a beam B of a second node;
a processing module 620, configured to determine, based on the
first adjustment time period, the transmission time in which the
downlink data is transmitted to the first terminal device by using
the beam A; and
a sending module 630, configured to send the downlink data to the
first terminal device by using the beam A based on the transmission
time.
Optionally, the obtaining module 610, the processing module 620,
and the sending module 630 are configured to perform operations of
the wireless communication method 300 in the embodiments of this
application. For brevity, details are not described herein
again.
FIG. 17 is a schematic block diagram of a terminal device 700
according to an embodiment of this application. As shown in FIG.
17, the terminal device 700 includes:
a processing module 710, configured to determine a first delay
difference between receiving a downlink pilot signal from a beam A
of a first node and receiving the downlink pilot signal from a beam
B of a second node, where the terminal device is located in a
coverage area in which the beam A intersects with the beam B;
and
a sending module 720, configured to send the first delay difference
to a control device, so that the control device predicts, based on
the first delay difference, a delay difference between receiving,
by the terminal device, downlink data from the beam A of the first
node and receiving, by the terminal device, the downlink data from
the beam B of the second node.
Optionally, the processing module 710 and the sending module 720
are configured to perform operations of the wireless communication
method 400 in the embodiments of this application. For brevity,
details are not described herein again.
FIG. 18 is a schematic block diagram of a communications device 800
according to an embodiment of this application. The communications
device 800 includes:
a memory 810, configured to store a program, where the program
includes code;
a transceiver 820, configured to communicate with another device;
and
a processor 830, configured to execute the program code in the
memory 810.
Optionally, when the code is executed, the processor 830 may
implement the operations performed by the control device in the
method 200. For brevity, details are not described herein again. In
this case, the communications device 800 may be a receiving device
or a sending device. The transceiver 820 is configured to receive
and send a specific signal after being driven by the processor
830.
Optionally, when the code is executed, the processor 830 may
alternatively implement the operations performed by the node in the
method 300. For brevity, details are not described herein again. In
this case, the communications device 800 may be a receiving device
or a sending device.
Optionally, when the code is executed, the processor 830 may
alternatively implement the operations performed by the terminal
device in the method 400. For brevity, details are not described
herein again. In this case, the communications device 800 may be a
receiving device or a sending device.
It should be understood that in this embodiment of this
application, the processor 830 may be a central processing unit
(CPU), or the processor 830 may be another general-purpose
processor, a digital signal processor, an application-specific
integrated circuit, a field programmable gate array or another
programmable logic device, a discrete gate or a transistor logic
device, a discrete hardware component, or the like. The
general-purpose processor may be a microprocessor, or the processor
may be any conventional processor, or the like.
The memory 810 may include a read-only memory and a random access
memory, and provide an instruction and data to the processor 830. A
part of the memory 810 may further include a nonvolatile random
access memory. For example, the memory 810 may further store
information of a device type.
The transceiver 820 may be configured to implement a signal sending
and receiving function such as a frequency modulation and
demodulation function or an up-conversion and down-conversion
function.
In an implementation process, at least one step in the foregoing
methods may be completed by an integrated logic circuit of hardware
in the processor 830, or the integrated logic circuit may complete
the at least one step after being driven by an instruction in a
form of software. Therefore, the communications device 800 may be a
chip or a chip group. The steps in the methods disclosed with
reference to the embodiments of this application may be directly
performed by a hardware processor, or may be performed by using a
combination of hardware in the processor and a software module. The
software module may be located in a mature storage medium in the
art, such as a random access memory, a flash memory, a read-only
memory, a programmable read-only memory, an electrically erasable
programmable memory, or a register. The storage medium is located
in the memory. The processor 830 reads information in the memory
and completes the steps in the foregoing methods in combination
with the hardware of the processor 830. To avoid repetition,
details are not described herein again.
It should be understood that sequence numbers of the foregoing
processes do not mean execution sequences in various embodiments of
this application. The execution sequences of the processes should
be determined based on functions and internal logic of the
processes, and should not be construed as any limitation on the
implementation processes of the embodiments of this
application.
It may be clearly understood by a person skilled in the art that,
for the purpose of convenient and brief description, for a detailed
working process of the foregoing system, apparatus, and unit, refer
to a corresponding process in the foregoing method embodiments.
Details are not described herein again.
The foregoing descriptions are merely specific implementations of
this application, but are not intended to limit the protection
scope of this application. Any variation or replacement readily
figured out by a person skilled in the art within the technical
scope disclosed in this application shall fall within the
protection scope of this application. Therefore, the protection
scope of this application shall be subject to the protection scope
of the claims.
* * * * *